DESCRIPTION: The underlying cause of cataracts can often be shown to involve defects in lens fiber cell differentiation. The proposal seeks to elucidate the mechanisms controlling the high level, lens-specific expression of the bB1 crystallin gene, a crystallin expressed exclusively in differentiating lens fiber cells. The aims of the proposal are to determine the role of the Prox-1 homeodomain protein in activation of the bB1 gene, to determine the role of Pax6-mediated repression of bB1 promoter in fiber cell differentiation, to identify other transcription factors that are involved in regulating expression of the bB1 gene and finally to identify sequences in the bB1 crystallin gene promoter that are required for appropriate spatial and temporal expression of bB1 crystallin during fiber cell differentiation.